Cardiomyocytes have mosaic patterns of protein expression.

Skeletal myocytes have well-established fast and slow twitch fibers with unique gene and protein specific expression patterns. By immunohistochemical staining, these show a mosaic pattern across myocytes. We hypothesized cardiac myocytes may behave similarly where some proteins are differentially expressed between mature cardiomyocytes. We utilized the tool HPASubC on over 52,000 cardiac images of the Human Protein Atlas to identify differential protein expression patterns by immunohistochemistry across the cardiomyocytes. We matched identified proteins to open chromatin and gene expression data. We identified 143 putative proteins with mosaic patterns of expression across the cardiomyocytes. We validated four of these proteins (MYL3, MYL4, PAM, and MYOM1) and demonstrated unique atrial or ventricular patterns of expression for each. Acetylation of histone H3K27 at the promoters of these four genes were consistent with the atrial/ventricular expression patterns. Despite the generally accepted homogeneity of cardiomyocytes, a small subset of proteins varies between cardiomyocytes in a mosaic pattern. This fundamental process has been previously uncharacterized. These changes may inform on different functional and disease-related activities of proteins in individual cardiomyocytes.

Peptide amidating activity in human bronchoalveolar lavage fluid: relationship to lung cancer, inflammation and infection.

The most common post-translational modification of peptide hormones, present in half of all neuroendocrine (NE) peptides, is alpha-amidation and this is necessary for the biological activity of the peptides. Peptides are alpha-amidated by the action of two enzymes: peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidylamidoglycolate lyase (PAL). As the common pathway for the formation of amidated peptides, the enzymes may provide a better indication of the NE status of a tumour or tissue than the presence of any single amidated peptide. PHM and PAL enzyme activities were measured in 39 BL fluid specimens from patients undergoing bronchoscopy for diagnosis of lung cancer. The assays revealed that PHM levels were higher in a group of specimens from patients undergoing bronchoscopy for chest infection, inflammation, asthma, or pneumonia compared to a group of specimens in which malignant cells were seen. The presence of elevated levels of amidating enzymes in specimens with non-cancerous conditions may reflect events of promotional phase cancer biology occurring simultaneously with inflammatory and infectious processes.